The purpose of this study was to determine whether gonadotropin-releasing hormone agonist further increases the prolactin rise accompanying ovarian stimulation.Serum prolactin concentrations were compared between cycles with and cycles without the use of leuprolide acetate (LA) matched for estradiol levels. Relationships of prolactin levels to cycle outcomes were examined.The study took place at a private fertility center.Patients were women receiving stimulation for oocyte retrieval using human menopausal gonadotropins.No interventions were used.Serum prolactin level, fertilization rate, embryo quality, and pregnancy were the main outcome measures.Higher serum prolactin was associated with both higher estradiol levels and use of LA but did not have any effects on fertilization rate, embryo quality, or occurrence of pregnancy.LA stimulates prolactin release during ovarian stimulation but without apparent consequence.